This invention relates to rotating or moving metal components and methods of manufacturing such components. In particular it is concerned with rotating blades or parts of such blades suitable for gas turbine engines although the invention may be applicable to other types of engines. It may be particularly suitable for application to blades used in the compressor stage of a gas turbine engine. The invention may also be employed for the manufacture of e.g. gears where the teeth are required to be made of steel but where the remainder of the component gear is made of titanium or light alloy to reduce the rotating mass.
Certain kinds of gas turbine engine employ titanium alloy blades and discs in the compressor stage of the engine. The tip of each blade is designed to run in close proximity to a casing or an ablative lining on the casing. During certain aspects of engine operation, contact is possible and in some cases inevitable between the tip of the blades and the casing or its lining. In extreme conditions incidents of this type could result in frictional heating of the tip and the presence of titanium or titanium alloy dust being emitted from the titanium alloy blade tip. Such tip heating and titanium alloy dust emitted from the tip of a blade in a compressor could in theory result in ignition and propagation of fire in the titanium blades themselves.
It is one object of the invention to provide a blade and a method of manufacturing such a blade which would reduce or eliminate the likelihood of such ignition taking place.